Spectro-Microscopy Methods To Gain a Multimodal Perspective.

Combining spectroscopic techniques with spatially-resolved microscopy capabilities creates an avenue for in-depth investigations into understanding the impact of specific regions and features across surfaces and their relevance for resulting device performance. For device optimization and development, these techniques can be utilized as a means to identify the impacts and roles of the underlying defects and charge extraction across interfaces. Here, we highlight the ways that (correlated) spectro-microscopy methods have been utilized within the field of materials science to understand materials properties and the underlying optoelectronic processes dictating device functionality.

Intermolecular Interactions and their Implications in Solid-State Photon Interconversion.

Photon interconversion promises to alleviate thermalization losses for high energy photons and facilitates utilization of sub-bandgap photons - effectively enabling the optimal use of the entire solar spectrum. However, for solid-state device applications, the impact of intermolecular interactions on the energetic landscape underlying singlet fission and triplet-triplet annihilation upconversion cannot be neglected. In the following, the implications of molecular arrangement, intermolecular coupling strength and molecular orientation on the respective processes of solid-state singlet fission and triplet-triplet annihilation are discussed.

Upconversion on the Micrometer Scale: Impact of Local Heterogeneity.

The properties of perovskitenaphtho[2,3-]pyrene (NaPy) upconversion devices are investigated by a combination of atomic force microscopy and photoluminescence mapping to understand the role of microscopic heterogeneity in the ensemble device properties. The results emphasize strong microscopic inhomogeneity across the perovskite/NaPy upconversion device due to local formation of NaPy microcrystals. NaPy shows emission from three distinct states in the solid state: S' emission at 520 nm, excimer emission at 560 nm, and S″ emission at 620 nm.

Advances in Spectro-Microscopy Methods and their Applications in the Characterization of Perovskite Materials.

Perovskite materials are promising contenders as the active layer in light-harvesting and light-emitting applications if their long-term stability can be sufficiently increased. Chemical and structural engineering are shown to enhance long-term stability, but the increased complexity of the material system also leads to inhomogeneous functional properties across various length scales. Thus, scanning probe and high-resolution microscopy characterization techniques are needed to reveal the role of local defects and the results promise to act as the foundation for future device improvements.